396 • TRANSACTIONS OF THE WAGNER FREE 



to 20 fathoms. Variety permagnum, Caloosahatchie Pliocene, W. H. Dall. 

 The adult specimen from the Caloosahatchie agrees in every particular 

 with the recent specimens, except that it measures 19.5 mm. in height as 

 against less than half as much for the largest specimen of the recent shell 

 which has yet come to hand. As the recent form may grow larger than the 

 specimens yet received, and mere size does not seem to be a very weighty 

 specific character, I prefer to apply the same name to both. 



Calliostoma virginicum Conrad. 



Plate 18, figure 2. 



Zizyphinus virginicus Conrad, Geol. Rep. N. Carolina, 1875, Appendix, p. 22, pi. 4, fig. 4. 



Chesapeake Miocene of Suffolk, Va., Conrad; and near Yorktown, Va., 

 Messrs. Harris and Darton, of the U. S. Geological Survey ; Cape Fear River 

 inarls, Johnson. 



This fine species has been inadequately described and figured by Conrad, 

 and it was thought best to figure one of the Yorktown specimens, in order 

 that the species should be recognizable. 



The shell measures 13.0 mm. in height and slightly more in maximum 

 diameter. It has a channelled periphery with two strong, equal keels, rounded 

 and finely striated. The suture runs on the anterior keel, and has in front of 

 it (separated by a smooth space about as wide as the peripheral channel) a 

 single strong thread. This combination strongly accentuates the suture. The 

 space in front of the strong thread and extending to the periphery is con- 

 stricted or excavated, and sculptured with very fine, close, simple and sub- 

 equal spirals. The base has one or two strong threads about the umbilical 

 region, then finer ones extending to the periphery. There is a shallow groove 

 behind the pillar, but no perforation. The apex is rather blunt, the nucleus 

 small and smooth, and there are five or six turns. The specimens vary in propor- 

 tional height, some being less elevated, but the general character of the sculpt- 

 ure is very uniform. 



This species is really related to Mitchelli and philanthropus. The sup- 

 pression of the beading, the magnification of the sutural and peripheral keels, 

 and the presence of many fine, even spirals in place of fewer unequal ones, 

 are the modifications which would bring the forms together, and such modifi- 

 cations are not uncommon in the group, as we have already seen in the case of 

 the varieties of C. philanthropus. The following variety gives point to these 

 observations : 



Calliostoma (virginicum. var. ?) aluminium Dall. 



Chesapeake Miocene of the upper bed at Alum Bluff, Chattahoochee 

 River, Florida, Burns. 



A single specimen was obtained by Mr. Burns which recalls C. virgijiiann, 

 but differs from it in the following particulars : The sutural rib is strong and 



